If so what are they and what do they do?
There is a tree glitch in Giant Chasm where you can walk through some trees. It's up in the top left.
There are some more listed on Bulbapedia here including a surfable tree, grass tile on which you cannot encounter Pokemon, mail glitch that makes ability text disappear, duplicate N, and a PWT glitch.
You can surf in a tree at Pokestar Studios; the one at the rightmost and top a bit.